1. Field of the Invention
The present invention generally pertains to methods and systems for false alarm reduction in motion detection by scanning cameras.
2. Discussion of Related Art
Motion detection with scanning cameras suffers from a relatively high rate of false alarms. These false alarms can be caused by many factors such as stains on the camera glass, sun reflections, dead pixels in a thermal camera, etc., which induce virtual motion relative to the image that is not related to any real moving object in the area.
Another limitation of motion detection with scanning cameras involves the time duration needed by the system to decide that a moving object was detected. Due to the short time that an object is exposed to the camera during the scan, detection should be as fast as possible, otherwise, the object will disappear from the camera field of view before it is detected.
Unfortunately, the short detection time needed causes the system to be very sensitive to false alarms because there is not enough time to analyze the motion and to decide if the motion should be reported or is induced by nuisances such as moving trees that should be filtered out.
In order to provide a higher detection time for a given event, one must increase the time that the object is exposed to the camera by lowering the scan speed. This is an unacceptable solution because it reduces the system area coverage rate.
U.S. Pat. No. 4,337,481, entitled “Motion and intrusion detecting system”, describes a method to detect small and fast motion by a scanning cycle composed of 2 scans with different predefined speeds. This method does not give a solution to the long time duration needed to complete a cycle, nor to the false alarms caused by the virtual motions.
U.S. Pat. No. 4,814,779, entitled “Radar system with auxiliary scanning for more dwell time on target”, describes a method to use two interconnected radar systems to enable investigation of the target by the secondary radar while the primary radar is in a continuous scanning. This method is aimed to the area of radars where totally different problems are encountered.
Hence, methods and systems for false alarm reduction in motion detection with scanning cameras are still a long felt need.